In order that optical waveguides can be welded to one another by means of fusion welding, for example, the optical waveguides are uncovered in the vicinity of the locations to be welded. For this purpose, fiber coatings surrounding the optical waveguides are removed. After the optical waveguides have been welded to one another, for example, they are protected against ambient influences and mechanical damage. Protection for an exposed optical waveguide may also be necessary for other reasons.
A protective element shrinkable by means of the supply of heat is usually used for protecting a previously uncovered optical waveguide. The protective element is embodied as a tube made of a material shrinkable by means of the supply of heat, for example a polymer. The protective element is pushed over a section of the optical waveguide that surrounds the uncovered part, and is then heated. The heating brings about heat-shrinking of the protective element. After the heat shrinking, that section of the optical waveguide which surrounds the uncovered part is closely enclosed by the protective element. Furthermore, the protective element can adhere to the surface of the uncovered optical waveguide. The desired protection against ambient influences and mechanical damage is achieved in this way.
In order to heat a protective element shrinkable by means of the supply of heat, use is made of a so-called shrinking furnace. The shrinking furnace usually contains a trough with a u- or v-shaped channel for receiving the protective element and a heating element for heating the trough.
A conventional shrinking furnace has the disadvantage that the heat from the heating element is transferred to the protective element by thermal conduction via the trough and by convection via the air. Due to this indirect transfer of the heat from the heating element to the protective element, the temperature of at least one part of the trough and the temperature of at least one part of the air are always above the temperature of the protective element. The trough and the air in each case have a considerable thermal capacity. Therefore, a large part of the thermal output generated by the heating element is consumed for heating the trough and the air. Moreover, only a small part of the surface of the trough and a small part of the surface of the protective element touch one another. As a result, only small quantities of heat per unit time can be transferred directly from the trough to the protective element by thermal conduction.
Shrinking furnaces and corresponding fusion welding apparatuses which are supplied with power by means of batteries or accumulators are produced for mobile use. However, the conventional shrinking furnace wastes a considerable amount of the generated energy for heating the heating element, the trough and the air. This energy is no longer available for shrinking on protective elements or carrying out welding operations. Consequently, the number of shrinking-on and welding operations that can be carried out with a battery or accumulator charge is dramatically reduced.
In order to transfer the required quantity of heat to the protective element, the conventional shrinking furnace requires a corresponding time period. Approximately 45 seconds are required for the heating-up phase, in which the heating element, the trough, the air and the protective element assume the temperature necessary for initiating the shrinking-on. Approximately 45 seconds are also required for the shrinking-on phase, in which the protective element takes up, the thermal energy required for the shrinking-on process. The power consumption of the shrinking furnace is about 20 W during the heating-up phase and about 15 W during the shrinking-on phase. Accordingly, this results in an energy consumption of 900 Ws for the heating-up phase, an energy consumption of 675 Ws for the shrinking-on phase and a total duration of the shrinking-on operation of approximately 90 seconds.
Overall, it can be stated that the energy consumption and the time expended for shrinking a protective element onto an optical waveguide using a conventional shrinking furnace are unnecessarily high.
Accordingly, the object of the invention is to specify a device and a method for the rapid and energy-saving shrinking of protective elements onto elongated elements such as optical waveguides.